1. Field of the Invention
The present invention concerns the field of equipment for video teleconferencing and, more specifically, an improved design for a terminal that allows eye contact between a local conferee and a remote conferee at a second terminal.
2. Description of Related Art
Video-teleconferencing is now positioned to become as common as the telephone conversation. With the recent advances in video signal transmission inexpensive interactive video is quickly becoming a reality. The ability to transmit video, however, is only one necessary element to a successful teleconferencing system. One area of great importance that will determine the success of teleconferencing is the ability to have natural communication. Fundamental to human communication is eye contact. Present teleconferencing devices are unable to provide eye contact because a teleconferencing camera is placed beyond the perimeter of the display imaging the distant conferee to avoid visual interference with that display. With this configuration the conferees fail to look directly into the camera so that conferees appear to be looking away, disinterested in the conversation.
There have been several technologies proposed to correct the eye contact problem. The majority of these technologies require specialized displays that are configured so that a camera can be mounted behind the viewing surface of the display. A great drawback to these technologies is that they cannot be readily integrated with existing television and computer displays owned by consumers. Also, many of these technologies cannot be integrated with various display technologies such as direct view cathode ray tube, plasma display panel, and field emitter display because these devices do not permit a camera to be mounted behind their viewing surfaces. Eye contact can also be achieved through image processing techniques. The drawback to image processed eye contact is that advanced computer hardware and software adds, at present, a significant expense to a teleconferencing terminal.
One of the best-known eye contact technologies is also the most flexible in being combined with various display technologies. A beam-splitter consisting of a half-silvered mirror, when placed at a roughly 45-degree angle in front of any display, will permit light from that display to pass through and be observed by a conferee. Simultaneously, that conferee's image can be captured by a camera placed to capture the image of that conferee reflected in the half-silvered mirror. Even though this technology can be configured in front of the viewing surface of nearly any display, the awkward protrusion of the half-silvered mirror renders the technology clumsy at best. Not only does the protrusion use up a considerable amount of space, but also, the conferee imaged on the display appears to be recessed deep into the terminal, augmenting awareness of distance between conferees.
Another beam-splitter arrangement is similar to this previous technology except the display and camera are reversed and used in a similar manner as a teleprompter. Here the camera is mounted behind the half-silvered mirror and the viewing surface of the display is aimed toward the half-silvered mirror which reflects the display's image. Because the half-silvered mirror is angled at roughly 45 degrees, this configuration suffers from the same drawbacks as the technology previously mentioned.
In an attempt to minimize the drawbacks of these beam-splitter technologies, U.S. Pat. No. 5,117,285 to Nelson teaches the use of a polarizer added to a beam-splitter consisting of a partially-silvered mirror to reduce the protrusion of the partially-silvered mirror from 45 degrees to roughly 30 degrees. The use of polarizers permits the camera to be positioned at an angle where light from the display would normally, without polarizers, prevent quality image reflection. A significant drawback to this technology is that the protrusion of the partially-silvered mirror is not reduced sufficiently for practical use, especially for larger displays. Also, the camera in this arrangement awkwardly protrudes from the base of the display. Another significant drawback is that the addition of polarizers reduces the brightness of the display, greatly reducing image quality.